Monitoring bands during the Norwegian national day parade: a case study on urban distributed acoustic sensing

Existing networks of fiber optic telecommunication infrastructure can be used to measure acoustic events. For this purpose, a laser instrumentation is attached to a "dark fiber" turning it into a Distributed Acoustic Sensing (DAS) device. In May 2023, a DAS test was conducted to measure acoustic activity in Oslo, Norway. The main purpose was to measure the "pulse" of the Oslo city center during the Norwegian National Day parade. Additionally, five days before and after the National Day were recorded for reference to daily acoustic background noise conditions in Oslo. Data during the National Day captured the yearly parade in which schools and bands participate. Using this data, it was possible to detect the participating bands, analyze their frequency content, and estimate their walking speed and step length. High-order harmonics were recognized in the frequency response for the bands. A total of 88 bands participated in the parade and 87 were detected using the harmonic characteristics. While one individual band could be tracked before the main parade over separate streets, it was challenging to continue the track for other bands within the parade. The test revealed that DAS can be used as part of decision support systems for crowd monitoring.